Regarding his supplication, Allah says:
رَبِّ اشْرَحْ لِي صَدْرِي ﴿٢٥﴾ وَيَسِّرْ لِي أَمْرِي ﴿٢٦﴾ وَاحْلُلْ عُقْدَةً مِّن لِّسَانِي ﴿٢٧﴾ يَفْقَهُوا قَوْلِي ﴿٢٨﴾
Pronunciation
Rabbish-rah lee sadree. Wa yassir leee amree. Wahlul 'uqdatam-mil-lisaanee. Yafqahoo qawlee.
Meaning
My Lord, expand for me my breast [with assurance] (25) And ease for me my task(26) And untie the knot from my tongue(27) That they may understand my speech.(28)
Source: Surah Ta Ha 20: 25-28
Duas from IslamicAPI's Masnun Dua dataset (based on the Quran, hadith, Hisnul Muslim and Rahe Belayat). See the dataset